Exposure, Not Route: Cardiovascular Pharmacology of Oral versus Injectable GLP-1 Receptor Agonists
Year: 2026
Type: preprint
Abstract: This research project is a narrative review examining whether the cardiovascular effects of glucagon-like peptide-1 receptor agonists (GLP-1RAs) differ according to route of administration, with particular emphasis on oral versus injectable therapy. The review addresses the emerging transition from predominantly injectable GLP-1RAs toward orally administered agents, including oral semaglutide and the newer non peptide oral GLP-1 receptor agonist orforglipron. The primary purpose of this review is to evaluate the hypothesis that the cardiovascular effects of GLP-1 receptor agonism are primarily exposure-dependent rather than intrinsically route dependent. The review therefore examines whether an oral GLP-1RA that achieves adequate and reliable receptor exposure should reproduce the cardiovascular benefits observed with injectable therapy. Particular attention is given to differences in pharmacokinetics and pharmacodynamics, including bioavailability, dose-to-dose variability, dosing interval, peak-to-trough dynamics, achieved exposure, titration, and adherence. The review synthesizes evidence across several cardiovascular domains, including major adverse cardiovascular events, atherosclerotic cardiovascular disease, heart failure with preserved ejection fraction, renal outcomes, heart rate, and blood pressure. Evidence from major cardiovascular outcome trials of injectable GLP-1RAs is considered alongside evidence from oral semaglutide trials, particularly PIONEER-6 and SOUL. The review also examines the relevance of the OASIS and STEP programmes to the relationship between oral and injectable exposure and the magnitude of weight loss. A specific component of the review evaluates the route specific effects of the absorption enhancer sodium N-(8-[2-hydroxybenzoyl]amino)caprylate (SNAC), which is co-administered with oral semaglutide. The review considers whether transient epithelial permeability induced by the enhancer could theoretically influence intestinal barrier function, endotoxin translocation, inflammation, and cardiovascular risk. This potential mechanism is assessed alongside the counter-regulatory effects of GLP-1 receptor agonism on intestinal barrier integrity, chylomicron-mediated endotoxin trafficking, and systemic inflammation. The review further considers heart failure with preserved ejection fraction as a distinct clinical domain because the gastrointestinal tract may be affected by congestion and altered physiology in this population. It identifies the absence of dedicated oral GLP-1RA outcome and functional trials in HFpEF as an important evidence gap and proposes specific hypotheses concerning exposure variability, intestinal barrier function, and inflammatory markers in this setting. The expected outcome of the review is a structured assessment of whether current evidence supports exposure rather than route as the principal determinant of cardiovascular benefit from GLP-1 receptor agonism. The review is expected to identify areas where oral and injectable therapies demonstrate concordant cardiovascular effects, distinguish established evidence from cross trial inference, and define the remaining uncertainties. The review also proposes a research agenda for future studies, including exposure-matched oral versus injectable comparisons, domain-specific cardiovascular and HFpEF endpoints, prospective assessment of heart rate and blood pressure, mediation analyses incorporating achieved exposure and weight loss, and measurement of intestinal permeability and endotoxemia markers. Overall, the project aims to clarify whether oral administration represents primarily an alternative delivery route for an established cardiovascular pharmacology or whether route-specific pharmacological effects require independent evaluation.
Authors: Jeel Padaria, Abiya Ahad, Darshan Hullon
Language: English
Subfield: Endocrinology, Diabetes and Metabolism
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W7204692989